Role of temperature on colloidal behavior of gold nanoparticles dispersed in organic and aqueous media

Abstract

Gold nanoparticles (AuNPs) are considered as one of the most stable metal nanoparticles and have received immense research’s interest due to their size-related electronic, magnetic and optical properties such as quantum size impact. However, AuNPs tend to form agglomeration in solution. Hence, detailed study on colloidal stability is crucial in preventing the agglomeration of AuNPs. The AuNPs was prepared by using sodium citrate reduction method before dispersing the sample in the organic media, dimethylformamide (DMF) prior to transmission electron microscopy (TEM) and Zeta Sizer analysis. The AuNPs were also dispersed in aqueous media which subsequently being characterized using UV-Vis spectroscopy and Zeta Sizer analysis. The effect of temperature was investigated in order to identify the hydrodynamic size and the stability of the AuNPs in both DMF and aqueous media. The presence of AuNPs in solution was confirmed by the maximum absorbance peak at the wavelength of 552 nm. From the TEM analysis, the AuNPs were dispersed well in the organic media which the nominal particles size distribution centered at 3.5 nm. The optimum temperature for AuNPs in both organic and aqueous media was at ≤ 35 °C where the zeta potential showed -30.7 mV and -36.7 mV respectively. From the observations on hydrodynamic particles size, it was shown that the particles size had the smallest size of 20 nm at 25°C and biggest size of 132 nm at 55°C in aqueous media. While particles size in DMF showed, the smallest size and biggest size were 36 nm at 25°C and 158 nm at 55°C, respectively. Thus, the AuNPs in aqueous media showed comparatively smaller size of particles compare to the AuNPs in DMF.